Community Ecology in Lakes

Question 1

What is the HSS model?

Answer 1

Depending on how many trophic levels there are, the limiting factor could be resources or predation. This depends on the cascading effect.
E.g. if there is only primary production (one level) the limiting factor is resources, but if there are planktivors present then the predation will be the limiting factor.

Question 2

What is the size efficiency hypothesis?

Answer 2

The larger zooplankton (such as daphnia) are more efficient grazers.

Question 3

What is ontogenic niche shift?

Answer 3

When an organism (usually predators) change diet selectivity as they grow.

Question 4

Name an example of behaviorally -mediated trophic cascade.

Answer 4

Prey exhibit a behavioral response to predators – seek refuge, hide.
This behavioral response reduced prey feeding rates and causes a trophic cascade.

Question 5

What determines primary production in top down? And in bottom up?

Answer 5

• Bottom-up: Nutrient (P) availability
• Top-down: Number of trophic levels

Question 6

What determines food chain length?

Answer 6

• Productivity of the primary producers
• Ecosystem size
• Productive space

Question 7

There are 3 ways of switching to an alternative stable state, what are they?

Answer 7

• Smooth transition
• Abrupt transision
• Hysteresis